I know it's been discussed before but how much should I cut of the frame to get the board to lean back for faster forward flight.

Nip about 1/16" off and push the board back against the post you cut off. If it looks good, put the screw in. If you need a bit more, trim it again. I cut 1/8" off and that was a bit too much. I put a cardboard shim between the board and the post. If you cut off a bit too much that will fix it.